Internal illumination based sign device

ABSTRACT

An illuminating unit ( 28 ) is presented for use in an internally illuminated sign device ( 1 ) for displaying a pattern indicative of certain fixed information within an indicia area. The illuminating unit ( 28 ) comprises a light boundary structure ( 33 ) for a light source ( 38 ) to be mounted thereon. The light boundary structure ( 33 ) has an indicia area carrying side ( 16 ) having said pattern indicative of the information to be displayed, and has an inner surface made of at least one highly reflective material to thereby increase the amount of light propagating from the light source ( 38 ) to said indicia area

FIELD OF THE INVENTION

This invention is generally in the field of sign devices, and relates toan internal illumination based sign device. The present invention isparticularly useful as an outdoor sign device, for example as a housenumber sign.

BACKGROUND OF THE INVENTION

Indoor and outdoor illuminated signs are known devices widely used allover the world for orientation, advertising and other purposes, and aretypically installed in public places where a large number of people cansee them. Many signs need to be visible at night and this is oftenaccomplished by internally illuminating the information (indicia)presented on a sign panel. Various techniques are used to construct asign device with substantially uniform illumination of the indicia.

Most of the conventional devices of the kind specified utilizefluorescent tubes or incandescent lamps as light sources, which arecharacterized by up to a 360°-spread of generated light. A light boxutilizing such a light source is typically equipped with reflectors anddiffusers so as to prevent the creation of “hot spots” and regions ofexcessively greater than average illumination, and to obtain uniformdistribution of light impinging onto the inner surface of the frontpanel. This results in a drastic reduction in the amount of lightemerging from the front, indicia-containing panel of the device towardsthe viewer.

Internally illuminated sign devices utilizing light emitting diodes(LEDs) as light sources have been developed, and are disclosed, forexample, in U.S. Pat. Nos. 5,105,568; 5,539,623; 5,388,357; 5,729,925;and 4,952,023. According to U.S. Pat. No. 5,105,568, a plurality of LEDsis aligned along all the parts (letters) of textual information, andhigh reflective elements are provided on selective areas of the innersurface of the sign panel. According to U.S. Pat. No. 4,952,023,reflectors are used in the optical path of light propagating inside thelight box towards the sign panel.

Illuminated house signs are generally installed on the outside of thehome to show a family name and/or house number and street name. Suchsigns need to be reasonably priced and suitable for mass production.Such a sign device also needs to be custom-made so as to carry a uniquefamily name and/or a specific house number. Conventionally, this isachieved by making an illuminating box wide enough to encompass severalletters and/or numerals, and using a mask, which is supplied insufficient duplicates of letters and/or numerals to create the specificindicia (address and/or name). When in operation, the mask covers theilluminating box to create indicia showing the desired house number,address or family name.

SUMMARY OF THE INVENTION

There is a need in the art to improve the operation of internalillumination based sign devices, by providing a novel illuminating unit,power supply unit, and sign device utilizing the same.

There is also a need in the art for a modular house sign device that iscustom-made without the need for customized manufacture.

Sign devices need to be easy to mount by the purchaser himself withoutthe need for a specialist's assistance. They also need to resistenvironmental hazards such as sun radiation, humidity and rain, etc. toensure continuous and reliable operation.

The device of the present invention provides for effective internalillumination of an indicia area by maximizing the amount of light from agiven source reaching the indicia area; effective use of a solar cellpanel; and easily assembling the custom-made indicia area within thedevice.

There is thus provided according to one aspect of the present invention,an illuminating unit for use in an internally illuminated sign devicefor displaying a pattern indicative of certain fixed information withinan indicia area, the illuminating unit comprising a light boundarystructure for a light source to be mounted thereon, wherein said lightboundary structure has an indicia area carrying side having saidpattern, and has an inner surface made of at least one highly reflectivematerial to thereby increase the amount of light propagating from thelight source to said indicia area.

The light boundary structure defines a light containment vessel(volume). Such a vessel may be shaped like a box (i.e., the so-called“light box”). It should be understood that the term “light box” usedherein signifies a closed structure, which may or may not have arectangular cross-section, and may or may not be integral, provided itdefines at least one indicia carrying side, patterned in accordance withsaid information to be displayed. The indicia pattern is formed bytranslucent regions surrounded by non-translucent regions, which, at theinner surface of the indicia carrying side, are surrounded by the highlyreflective regions.

For example, such a light boundary structure may be a six-sided box(one- or two part) having a four or five-sided frame (rigid, orflexible, or tape-like), attachable to, respectively, a single indiciaarea-carrying side or two opposite indicia-carrying sides. As for thesidewalls of such six-sided box, they may have straight or curvedsurfaces (e.g., formed by two or more facets with sharp or truncatedcorners).

The term “highly reflective material” used herein signifies a highlydiffusive (scattering) material or specularly reflective material.

The light source preferably comprises at least one light emitting diode(LED), which is preferably mountable aside the indicia carrying side.For example, one or more LED may be mounted on the side wall(s) of thesic-sided light boundary structure.

The indicia-carrying side may be removably mountable onto the lightboundary structure. By this, a selected indicia area can be mounted inthe illuminating unit.

The indicia-carrying side may be formed by a first panel patterned inaccordance with the information to be displayed and having the highlyreflective regions at its inner surface, and a second panel facing theinner surface of the first panel. In this case, the second panel is madeof a translucent material. The first panel may be removably mountableonto the second panel of the indicia-carrying side of the light boundarystructure. The light boundary structure may be a two-part structureformed by this second panel and a frame attachable thereto.

Preferably, the highly reflective material within the inner surface ofthe indicia-carrying side is diffusive, and the other inner surfaceoutside the indicia carrying side is specularly reflective.

According to another aspect of the present invention, there is providedan internally illuminated sign device for displaying a patternindicative of certain fixed information within an indicia area, thedevice comprising an illuminating unit having a light boundary structurefor a light source to be mounted thereon, said light boundary structurehaving an indicia area carrying side, and an inner surface made of atleast one highly reflective material to thereby increase the amount oflight propagating from the light source to said indicia area.

According to yet another aspect of the present invention, there isprovided an internally illuminated sign device for displaying a patternindicative of certain fixed information within indicia areas, the devicecomprising an illuminating unit having a light boundary structure for alight source to be mounted thereon, wherein the light boundary structureis a closed structure formed by two indicia area carrying sides, theinner surface of said structure containing at least one highlyreflective material to thereby increase the amount of light propagatingfrom the light source to each of the indicia areas.

The sign device preferably comprises a power supply source having abattery assembly connectable to the light source. This power supplysource preferably comprises a switching circuit for controlling theoperation of the battery assembly.

The switching circuit may comprise a connector shiftable between itsoperative and inoperative positions, such that when in the operativeposition, the connector actuates the battery assembly, and when in theinoperative position, prevents the battery assembly from being actuated,thereby enabling to keep the battery assembly disconnected when thedevice is not in use.

The switching circuit may comprise a battery recharge circuit operableto selectively disconnect the battery assembly from the light source,and/or recharge the battery assembly, in which case the switchingcircuit comprises a voltage limiting circuit operable to limit voltagecreated by the solar cell circuit to thereby provide a desired inputvoltage to the battery assembly. Preferably, the switching circuitcomprises a current adjusting circuit operable to provide a constantelectric current through the light source.

Thus, according to yet another aspect of the present invention, there isprovided a power supply source for use with an internally illuminatedsign device to supply power to a light source, the power supply sourcecomprising a battery assembly and a switching circuit for controllingthe operation of the battery assembly to provide at least one of thefollowing effects: selective connection and disconnection of the batteryassembly to and from the light source; recharge of the battery assembly;supply of a constant electric current to the light source.

BRIEF DESCRIPTION OF THE DRAWINGS

In order to understand the invention and to see how it may be carriedout in practice, preferred embodiments will now be described, by way ofnon-limiting example only, with reference to the accompanying drawings,in which:

FIG. 1 illustrates a sign device according to the invention exemplifiedas a house-number sign device;

FIG. 2 more specifically illustrates the construction of theilluminating and lower supply units of the device of FIG. 1;

FIG. 3 illustrates the light propagation scheme utilized in theilluminating unit according to the invention;

FIG. 4 exemplifies an indicia area containing side or panel suitable tobe used in the illuminating unit of the present invention;

FIGS. 5A-5B illustrates electronic circuitry suitable to be used in thepower supply unit of and the present invention; and

FIG. 6 illustrates a double-side sign device according to the presentinvention.

DETAILED DESCRIPTION OF THE INVENTION

Referring to FIG. 1, there is illustrated an internally illuminated signdevice 1 according to the invention. In the present example, the device1 is a house-number sign device, but it should be understood that it maybe any outdoor on indoor sign device of the kind utilizing internalillumination of an indicia area, i.e., a specific pattern indicative ofcertain fixed information (numeral “9” in this specific example).Additionally, in the present example, the sign device utilizes a solarcell based power supply source.

The device 1 comprises two functionally different units, an illuminatingunit 28 and a power supply unit 30, which are encompassed in a commonhousing, which, in the present example, is composed of a frontframe-like structure 10 and a rear cover 12. The housing (its frame 10)has, in its upper part, a window 14 for viewing therethrough an indiciaarea carrying panel 16. The panel 16 can be removably mounted in thedevice 1 by inserting it into the window 14, for example via tracks 18.The frame 10 has one or more holes 20 (two such holes in this specificexample) for securing the device 1 to a holding surface 22 (e.g., thehouse wall). Located at the lower part of the frame 10 is a furtherwindow 24, exposing therethrough a solar cell panel 26 (having one ormore solar cells).

The illuminating unit 28 (also referred to as a “light box”) is disposedwithin the upper part of the housing, and the power supply unit 30 isdisposed within the lower part of the housing. The operation of thelight box 28 and of the power supply unit 30, will be explained lateron. It should be understood that the invention is not limited by thisspecific example utilizing a two-part housing, rigid frame, anddisposition of the illuminating and power supply units at upper andlower parts of the device, and any other suitable arrangement can beused for the purposes of the present invention. For example, theilluminating and power supply units could be mounted in separate casesconnectable to each other, or the elements of these functional units maybe incorporated in a common unit.

In this specific example, the sign device 1 utilizes the solar energybased power supply, and for these purposes, the device has a curvedshape or at least curved front surface (for example like an “openV-shape” or arch shape). Hence, when the device is in use, i.e., isappropriately secured to the support surface, the indicia area carryingpanel is exposed to viewers, while the solar panel is inclined upward(with respect to the vertical plane) so as to collect more global solarradiation (as compared to its vertical position). Preferably, the lightbox 28 or at least the indicia area carrying panel 16 is slightly tiltedforward (i.e., inclined with respect to the vertical plane) so as toreduce glare in direct sunlight.

It should also be noted that in this specific example of FIG. 1 thedevice 1 is the single-sided sign device (with the indicia area on itsone side only). When a double-sided sign device is to be used, thedevice should be designed so as to be mountable by its sidewall onto asupport surface. The construction of the double-sided sign device willbe described more specifically further below with reference to FIG. 6.Generally, for the sign device, it may have any shape other than abox-like shape, provided it defines a closed structure serving as alight container and having an indicia area carrying surface.

As further shown in FIG. 1, the housing (its frame 10) has recesses 32on one side, and preferably also corresponding knobs (not seen) at theopposite side. This arrangement of recesses and knobs allows connectingthe device 1 to one or two similar devices, each independently operableto display its own information, and thereby create a modular signstructure for displaying multi-symbol information.

It should be understood that by providing an appropriate recess-and-knobarrangement, various combinations of attachments between severalindependent sign devices (modules) are made possible for creatingvarious signs, such as straight and/or diagonally patterned signs, etc.It should also be understood that the provision of recesses and knobs isoptional and any other arrangement is possible to provide a modular signstructure. Alternatively, it is not mandatory to use such arrangementsand the separate devices can be adjacently affixed to the supportsurface in an appropriate order defined by the user and the informationto be displayed.

The illuminating unit 28 according to the invention is designed toprovide highly efficient illumination of an indicia area (i.e., aspecific pattern indicative of certain fixed information to bedisplayed) by light generated by a light source (preferably one or moreLEDs) and provide a maximal amount of light exit to the viewer withuniform luminescence over the character face. This is achieved by makingthe inner surface of the illuminating unit from at least one highlyreflective material (except for translucent regions of the patternwithin the indicia area), such that this inner surface serves as a lightdirecting means for directing light generated by a light source towardsthe indicia area. Preferably, the inner surface of the indicia areacarrying panel or side contains diffusive material, and the innersurface outside the indicia carrying side contains specularly reflectivematerial.

The construction of the illuminating unit 28 is more specificallyillustrated in FIG. 2. The illuminating unit 28 presents a lightboundary structure, which, in the present example, has a box-likestructure 33, and utilizes the indicia area carrying panel 16(presenting the front panel of the unit 28) removably mountable onto thebox-like structure 33. The structure 33 in the present example is formedby two attachable parts: a rear frame 36 and an upper frame or panel 34.The indicia area carrying panel 16 is removably mountable onto the panel34, and these panels 16 and 34 present together the indicia carryingside of the light boundary structure 28. In the present example, theframes 34 and 36 are designed such that the frame 36 is mountable ontothe frame 34. As indicated above, the inner surface of the lightboundary structure is highly reflective (except for translucent regionsof the pattern within the indicia) and thus serves as the lightdirecting means for directing light generated by a light source towardsthe indicia area. The light source, which preferably utilizes one ormore LEDs (a single LED 38 being shown in the present example) ispreferably, supported aside the indicia area carrying side, and morepreferably on the sidewall(s) of the light boundary structure. To thisend, the structure 28 is formed with corresponding openings in theframes 34 and 36 for the LED 38 to be mounted therein so as to emitlight towards the inside of the structure 28. It should be noted thatgenerally LED(s) may be appropriately accommodated inside the boundarystructure, as well.

An LED of any known type and of any color can be used in the device ofthe present invention. Preferably LEDs having very high conversionefficiency (about 30 lumen per watt), low forward voltage, and colorstanding out clearly at dusk and/or in fog (where other colors are lessdiscemable) are used.

The indicia area (within which the number “9” is presented) is a patternformed by translucent regions TR which at the outer surface 16A of thepanel 16 are surrounded by light blocking or opaque regions BR, and atthe inner surface 16B of the panel 16 are surrounded by highlyreflective regions RR, which are preferably formed by a reflectivediffusive material, such as 3M Light Enhancement Film (LEF) or a highreflective printed layer. The other panel 34 of the indicia areacarrying side underlining the panel 16 is thus made of a translucentdiffusive material such as Polycarbonate or Acryl enhanced with adiffusive additive. As for the inner surface of the rear panel 36, it ispreferably specularly reflective (with reflectivity of more than 84%,for example polished aluminum sheet such as Alanod Miro-4 or Everbrite95). The operation of the light box 28 (i.e., the light propagationscheme) will be described farther below with reference to FIG. 3. Theindicia carrying panel or side can be manufactured as a multi-layerstructure, as will be described more specifically further below withreference to FIG. 4.

In the light boundary structure 28 of FIGS. 1 and 2, the sidewall (e.g.,intended for carrying the LED(s)) is a two-facet side. It should,however, be noted that a light boundary structure may have two oppositetwo-facet sides, two-face sidewall(s) with the facets arranged in aconcave or convex manner, straight sidewalls normal to the front andrear sides or inclined with respect to either the front or rear side, ormay have convex or concave rounded sidewall(s). Generally, the shape ofthe light boundary structure is selected in accordance with the indiciaarea dimension, the number of LEDs and their orientation, as well ashighly reflective materials used at the inner surfaces of the lightboundary structure, and the specific application of the device (i.e., tobe a single- or double-sided sign device). All these examples aresuitable for both the single-sided and double-sided sign device.

The sign device according to the invention is energy self-sufficient inthat it includes an autonomous power source unit 30, having a batteryassembly (including at least one battery) for supplying the LED withsufficient energy to ensure continuous and reliable operation, andpreferably also having the solar cell panel 26 (at least one solar cell)enabling the operation of the LED when needed (depending on the amountof ambient light in the vicinity of the sign device, and/or enablingrecharge of the battery). It should be noted that, generally, the solarcell can be replaced by any photoswitching device, such as photodiode.Thus, as exemplified in FIG. 2, the power supply unit 30 comprises thesolar cell panel 26 (for example comprising three tandem amorphouscells), the battery assembly 44, and a switching circuit 46 having anactivator switch 48. It should be noted although not specifically shown,that the power supply unit 30 may include more than one solar cellpanel, and may include the battery assembly 44 as the only power source.The power supply unit elements 26, 44 and 46 are mounted on the rearcover 12 of the housing and are supported by elements 50. The rear cover12 also has clips 52 that are used to attach the cover 12 to the frame10, and is formed with small windows 54 that permit air circulationwithin the device 1.

The batteries 44 can be supplied with the sign device or separately fromthe device. In the case of supplying the device with batteries (i.e.non-rechargeable batteries or rechargeable batteries that were chargedprior to installation into the device), the battery assembly isdisconnected in order to prevent the batteries from discharging. Inorder to provide initial actuation of the battery assembly when thedevice is out in operation, the switching circuit 46 includes aconnector jumper serving as an activator switch 48. The batteries areconnectable to an electronic circuit via the connector jumper 48, whichis implemented in the following manner. The connector jumper 48 isshiftable between its inoperative position being disconnected from theelectronic circuit and its operative position being connected to thecircuit so as to close the circuit with the battery. When the device isnot in use (say, between the time of manufacture and the time ofinstallation), the jumper connector 48 is not mounted in the switchingcircuit being kept together with the device as a separate element, andthe batteries 44 are thus disconnected from the electrical circuit beingthereby bound from discharging. When putting the device into operation,the jumper connector 48 is placed so as to be included in the electriccircuit, thereby closing the circuit with the battery, and shifting thedevice into its operative position for providing immediate illumination.When utilizing the device with attachable batteries, the device may notinclude a first-operation activator.

The battery assembly 44 may comprise rechargeable Alkaline Manganese(RAM) cells or rechargeable Pb/Pbo cells, having a minimalself-discharge rate. In this case, the circuit 46 is designed so as toenable the batteries 44 to be controllably charged by the solar cells.The switching circuit 46 may include a battery recharge circuit operableto recharge the battery (e.g., by means of the solar cell), and alsoincludes a voltage limiting circuit operable to desirably limit thevoltage supply to the battery from the solar cell.

The switching circuit 46 is designed for controlling the operation ofthe battery assembly 44 to provide at least one of the followingeffects: selective connection/disconnection of the battery assembly,recharge of the battery assembly (e.g., by means of a solar cell),supply of a constant electric current to the light source, and limit thevoltage supply to the battery from the solar cell. An example of theelectric scheme of the switching circuit 46 will be described morespecifically further below with reference to FIGS. 5A and 5B.

The rechargeable batteries may be supplied as pre-charged. In that case,the above-mentioned connector jumper 48 controls the first actuation ofthe device. If the rechargeable batteries are not pre-charged prior tobeing supplied with the device, the device when activated for the firsttime will immediately start solar charging but will effect illuminationonly after sufficient energy is gathered. Attachable batteries can besupplied separately from the device. In this case, the customer needs toinstall the batteries and to replace them by new ones from time to time.

In all the above-mentioned examples, the switching circuit 46 caninclude the battery recharge circuit (solar cell based circuit in thepresent example) for controlling the operation of the battery assemblyby selectively switching the batteries between ON and OFF stagesaccording to the solar cell state that depends on the amount of solarenergy in the vicinity of the solar cell panel. In addition, in all theabove-mentioned examples, the battery assembly, comprising eitherrechargeable batteries or not, can be replaceable.

Turning now to FIG. 3, there is illustrated the light propagation schemein the light boundary structure according to the invention (e.g.,structure 28 of FIGS. 1 and 2). In the present examples, the lightboundary structure is designed for a single-side sign device. As shown,the LED 38 is mounted on a sidewall of the light boundary structure suchthat it emits light substantially towards the opposite sidewall and theside opposite the indicia area carrying side 16. As shown in the figurein dashed lines, if no reflective coating was provided on the innersurface of the light boundary structure, a great amount of the emittedlight L_(em) would be lost. Due to the provision of this reflectivecoating, the emitted light impinging onto the specularly reflectiveinner surface is reflected back L_(ref) towards the pattern carryingpanel (e.g., while passing through the diffisive transmitting panel, asthe case may be), and those portions of this specularly reflected lightthat impinge onto the translucent regions TR of the indicia area emergefrom the structure, while the portions of the specularly reflected lightimpinging onto the diffusive reflective regions DT of the inner surfaceof the indicia carrying side are scattered back L_(scat) to the insideof the structure where they undergo further specular reflection and soon.

By making a proper choice of the light pattern distribution from theconcentrated light source, the number of reflections that a light raymust undergo until it exits the sign face can be minimized.

Additionally, selective use of high reflectance materials of differentreflective properties (i.e. specular vs. diffuse), can minimize thereflections, further increase the efficiency and provide even luminancealong the illuminated indicia area. Thus, if a light source with raysalmost parallel to the panel is distant from an exiting area (indiciaarea), then a specularly reflective material is used to allow the lightray to continue its propagation towards the indicia area without extrareflections. However, within the indicia area, a diffuse reflectingsurface affects the angle of reflection, such that the light ray has agreater chance of exiting through the proximate indicia openings(translucent regions). Thus, depending on the sign device arrangement(the dimensions of the indicia area, the number of LEDs and theirorientation), the inner patterned surface of the light boundarystructure (i.e., of its indicia area carrying panel or side) may be madeof a highly scattering material such as LEF, and the opposite innersurface of the light boundary structure and preferably also that of theside walls may be made of a specularly reflective material, such as 95%reflective aluminum.

As indicated above the indicia carrying panel or side (16 in FIGS. 1 and2) can be manufactured as a multi-layer structure. FIG. 4 schematicallyillustrates the manner of manufacturing such a structure. A substratelayer L₁, from which the translucent regions TR of the indicia patternare formed and which may be a foil plastic (e.g., polyester, PVC, etc.),is sequentially coated by a white opaque film L₂ in which the diffusivereflector regions DR of the inner surface of the panel 16 are formed(“negative printing”) and a layer L₃ in which the blocking regions BR ofthe pattern are formed on the outer surface of the panel 16 (“negativeprinting”) by using silk print colors. The patterning of thisthree-layer structure can be done in a single fabrication step, or in atwo-step process utilizing the same equipment This three-layer patternedstructure is coated by a layer L₄ of mat varnish (preventing thestructure from UV radiation), which may contain a flame retardingmaterial.

It should be noted, although not specifically shown, that for someapplications, the propagation of light emerging from the sign devicewith a specific solid angle segment of the entire 180°-space issufficient for the effective operation of the device. To this end, thesign device may comprise additional light directing means in the form ofa plurality of lenses located within the translucent regions of theindicia pattern. This can be implemented by making these regions of thetranslucent layer (basic layer L₁ in the structure shown in FIG. 4) witha specific surface relief acting as lenses.

Reference is made to FIG. 5A showing the switching circuit 46 suitableto be used in the power supply unit according to the present invention.As indicated above, the switching circuit 46 is designed for controllingthe operation of the battery assembly 44 to provide at least one of thefollowing effects: selective connection/disconnection of the batteryassembly, supply of a constant electric current to the light source,recharge of the battery assembly by means of a recharge circuit operableby a solar cell, and limit the voltage supply to the battery from thesolar cell. In the present example of FIG. 5A, the switching circuit 46is intended for use with the sign device that utilizes a replaceablebattery assembly that includes two pre-charged rechargeable batteries44, solar cell panel 26 and one LED-based light source 38, and isdesigned to carry out all these functions. It should, however, beunderstood that more LEDs can be used as well, the device of the presentinvention might not use a battery-based power supply, and might not usea solar cell for the battery recharge purposes.

Thus, in the present not-limiting example, the switching circuitcomprises the following functional elements: a connector jumper circuitSO1 (constituting the element 48 in FIG. 2) for the first actuation ofthe pre-charged battery assembly; a battery recharge circuit SO2operable by the solar cell 26 for recharge of the battery assembly andfor switching the battery operation between operative (ON) andinoperative (OFF) stages; a voltage limiting circuit VL for controllingthe input voltage to the battery assembly; and a current adjustingcircuit CC to provide the LED with a constant electric current.

The voltage limiting circuit VL can be implemented in severalconfigurations. In the specific example of FIG. 5A, the circuit VL isdesigned for efficient operation to prevent an unacceptable high voltage(above 1.7 volts for RAM batteries, for example) from being imposed oneither of the batteries. As shown in FIG. 5B, a less efficient voltagelimiting circuit VL′ can be used being implemented by directlyconnecting each of the emitting diodes D₁₁ and D₁₂ in parallel with itscorresponding battery. With respect to the circuit VL′ of FIG. 5B, thecircuit VL of FIG. 5A is more efficient as it allows for avoidingpotential losses due to leakage effects of the diodes.

The current adjusting circuit CC is operable by the recharge circuit SO2and is designed to provide the LED with a constant current while itsinput voltage varies due to the batteries' varying state of charge.

Turning now to FIG. 6, there is schematically illustrated how thepresent invention can be used in a double-side sign device. A signdevice 100 is designed to display specific information (a house numberin the present example) at its opposite indicia area carrying sides 100Aand 100B. In this example, similar to the example of FIGS. 1 and 2, thesign device utilizes a power supply source based on the use of a solarcell 26. Here, two LEDs 38 are used, but it should be understood thatgenerally a single LED can be used or an array of LEDs, which arepreferably mounted on the sidewall(s) of the light boundary structure.As shown in FIG. 6, the inner surfaces of the panels 100A and 100Bcontain diffusive reflective regions DR, and the inner surfaces of thesidewalls contain specularly reflective regions SR. The light impingingon each of the translucent regions TR of the indicia-carrying sidestherefore partly origins from the LEDs 38 (i.e. direct light) and partlyfrom the reflective regions SR and DR (i.e. reflected light).

It should be understood that the each of the panels 100A and 100B can beeither a single-part structure (e.g., a multi-layer structure asdescribed above with reference to FIG. 4), or a two-part structure as inthe example of FIGS. 1 and 2, wherein the upper part by which the deviceis exposed to the viewers is patterned and has a diffusive reflectivematerial at its inner surface and the lower part is made of a diffusivetranslucent material.

Those skilled in the art will readily appreciate that variousmodifications and changes can be applied to the embodiments of theinvention as hereinbefore exemplified without departing from its scopedefined in and by the appended claims.

1. An illuminating unit for use in an internally illuminated sign devicefor displaying a pattern indicative of certain fixed information withinan indicia area, the illuminating unit comprising a light boundarystructure for a light source to be mounted thereon, wherein said lightboundary structure has an indicia area having said pattern, and has ahighly reflective inner surface, the illuminating unit beingcharacterized in that the light boundary structure is formed of twoattachable parts including, respectively, a rear frame and an upperpanel structure removably mountable onto the rear frame, said upperpanel structure being a multi-layer structure formed by at least twolayers patterned in accordance with the information to be displayed, theupper external layer having translucent regions and light blockingregions of the indicia pattern, and the lower inner layer havingtranslucent regions and the highly reflective regions of the indiciapattern, to thereby increase the amount of light propagating from thelight source to said indicia area, enable replacing the indicia carryingpanel to display various information, and enable visibility of theindicia area via external reflected light.
 2. The illuminating unitaccording to claim 1, wherein the light source includes at least one LEDmounted inside the light boundary structure and oriented such that itemits light directly propagating onto the inner surface of the lightboundary structure opposite the indicia area carrying side of the lightboundary structure, to thereby increase the amount of light propagatingfrom the light source to said indicia area.
 3. The illuminating unitaccording to claim 1, wherein a portion of the highly reflective innersurface within the indicia area carrying side is made of a reflectivediffusive material.
 4. The illuminating unit according to claim 1,wherein a portion of said highly reflective inner surface locatedoutside the indicia area carrying side includes a specularly reflectivematerial.
 5. The illuminating unit according to claim 1, wherein saidlight boundary structure comprises a diffusive translucent layer locatedinside the structure underneath the indicia area carrying, side.
 6. Theilluminating unit according to claim 5, wherein said diffusivetranslucent layer is a foil plastic such as polyester or PVC.
 7. Theilluminating unit according to claim 1, wherein the multi-layerstructure is patterned in a single fabrication step.
 8. The illuminatingunit according to claim 1, wherein the multi-layer structure ispatterned in a two-step process utilizing the same equipment.
 9. Theilluminating unit according to claim 1, wherein the indicia areacarrying side has a protective coating made of mat varnish to therebyprevent said side from UV radiation.
 10. The illuminating unit accordingto claim 9, wherein said protective coating contains a flame retardingmaterial.
 11. The illuminating unit according to claim 1, wherein saidhighly reflective material within the inner surface of the indicia areacarrying side is reflective diffusive and includes 3M Light EnhancementFilm.
 12. The illuminating unit according to claim 1, wherein saidhighly reflective material of the inner surface of the light boundarystructure outside said indicia area carrying side is specular reflectiveand includes polished aluminum.
 13. The illuminating unit according toclaim 1, wherein the light source is mountable onto the light boundarystructure aside said indicia area carrying side.
 14. The illuminatingunit according to claim 1, wherein said light boundary structure is asix-sided box formed by the indicia carrying side, an opposite side, andside walls.
 15. The illuminating unit according to claim 14, wherein atleast one of the side walls has a curved surface.
 16. The illuminatingunit according to claim 15, wherein said curved surface is formed by atleast two facets.
 17. The illuminating unit according to claim 1,wherein a side of the light boundary structure opposite to said indiciaarea carrying side is also an indicia area carrying side patterned inaccordance with information to be displayed.
 18. The illuminating unitaccording to claim 14, wherein the light source comprises at least oneLED mountable onto at least one of the side walls of the light boundarystructure.
 19. The illuminating unit according to claim 18, wherein saidat least one LED is oriented such that it emits light directly onto theopposite side.
 20. The illuminating unit according to claim 1, whereinat least the indicia area carrying side of the light boundary structureis inclined downward with respect to a vertical plane so as to reduceglare in direct sunlight.
 21. An internally illuminated sign device fordisplaying fixed information, comprising the illuminating unit of claim1 and a power supply source connectable to the light source, whereinsaid power supply source comprises a battery assembly.
 22. The deviceaccording to claim 21, wherein said power supply source comprises aswitching circuit for controlling the operation of the battery assembly.23. The device according to claim 22, wherein said switching circuitcomprises a connector shiftable between its operative and inoperativepositions, such that when in the operative position the connectoractuates the battery assembly, and when in the inoperative positionprevents the battery assembly from being actuated, thereby enabling tokeep that battery assembly disconnected when the device is not in use.24. The device according to claim 22, wherein said switching circuitcomprises a recharge circuit operable to recharge the battery assembly.25. The device according to claim 21, wherein said battery assemblycomprises a solar panel.
 26. The device according to claim 25, whereinsaid solar panel is inclined upward with respect to a vertical plane soas to increase the amount of collected global solar radiation.
 27. Thedevice according to claim 25, wherein said switching circuit comprises asolar cell circuit, and is operable to selectively disconnect thebattery assembly from the light source.
 28. The device according toclaim 21, wherein said switching circuit comprises a voltage limitingcircuit operable to limit voltage created by the recharge circuit tothereby provide a desired input voltage to the battery assembly.
 29. Thedevice according to claim 21, wherein said switching circuit comprises acurrent adjusting circuit operable to provide a constant electriccurrent through the light source.
 30. The device according to claim 26,wherein said switching circuit comprises a solar cell circuit, and isoperable to selectively disconnect the battery assembly from the lightsource.
 31. An illuminating unit for use in an internally illuminatedsign device for displaying a pattern indicative of certain fixedinformation within an indicia area, the illuminating unit comprising alight boundary structure for a light source to be mounted thereon,wherein said light boundary structure has an indicia area having saidpattern, and has a highly reflective inner surface, wherein the lightsource includes at least one LED mounted inside the light boundarystructure and oriented such that it emits light directly propagatingonto the inner surface of the light boundary structure opposite theindicia area carrying side of the light boundary structure, to therebyincrease the amount of light propagating from the light source to saidindicia area.
 32. A power supply source for use with an internallyilluminated sign device to supply power to a light source, the powersupply source comprising a battery assembly and a switching circuit forcontrolling the operation of the battery assembly to provide at leastone of the following effects: selective connection and disconnection ofthe battery assembly to and from the light source; recharge of thebattery assembly by means of a solar cell circuit; supply of a constantelectric current to the light source.
 33. The power supply sourceaccording to claim 32, wherein said selective disconnection of thebattery assembly utilizes photoswitch element.
 34. The power supplysource according to claim 32, wherein said switching circuit comprises avoltage limiting circuit operable to limit voltage created by therecharge circuit to thereby provide a desired input voltage to thebattery assembly.
 35. An illuminating unit for use in an internallyilluminated sign device for displaying a pattern indicative of certainfixed information within an indicia area, the illuminating unitcomprising a light boundary structure for a light source to be mountedthereon, the light boundary structure having an indicia area with saidpattern and having a highly reflective inner surface, the illuminatingunit being configured such that at least the indicia area carrying sideof the light boundary structure is inclined downward with respect to avertical plane so as to reduce glare in direct sunlight.
 36. Aninternally illuminated sign device for displaying fixed information, thedevice comprising: an illuminating unit having a light source and alight boundary structure with an indicia area representative of thefixed information to be displayed; and a power supply source connectableto the light source and including a battery assembly that comprises asolar panel, the device being configured such that the solar panel isinclined upward with respect to a vertical plane so as to increase theamount of collected global solar radiation.